Pyrimido-benzimidazole derivatives and the use thereof in the form of agonists and antagonists of melanocortin receptors

ABSTRACT

The invention relates to novel pyrimido-benzimidazole derivatives. Said products exhibit a good affinity for certain melanocortin receptor sub-types, in particular MC4 receptors. Said products represent a particular interest for treating pathological disorders and diseases associated with one or several melanocortin receptors. Pharmaceutical compositions containing said products and the use thereof for a drug preparation are also disclosed.

FIELD OF INVENTION

A subject of the present application is novel pyrimido-benzimidazolederivatives. These products have a good affinity for certainmelanocortin receptor subtypes, in particular MC4 receptors. They areparticularly useful for treating pathological states and diseases inwhich one or more melanocortin receptors are involved. The inventionalso relates to pharmaceutical compositions containing said products andtheir use for the preparation of a medicament.

BACKGROUND OF INVENTION

The melanocortins represent a group of peptides which derive from thesame precursor, proopiomelanocortin (POMC), and which are structurallysimilar: adrenocorticotropic hormone (ACTH), α-melanocyte-stimulatinghormone (α-MSH), β-MSH and γ-MSH (Eipper B. A. and Mains R. E., Endocr.Rev. 1980, 1, 1-27). The melanocortins perform numerous physiologicalfunctions. They stimulate the synthesis of steroids by the adrenalcortex and the synthesis of eumelanin by the melanocytes. They regulatefood intake, energy metabolism, sexual function, neuronal regeneration,blood pressure and heart rate, as well as pain perception, learning,attention and memory. The melanocortis also possess anti-inflammatoryand anti-pyretic properties and control the secretion of severalendocrine or exocrine glands such as the sebaceous, lachrymal, mammaryglands, the prostate and the pancreas (Wikberg J. E. et al., Pharmacol.Res. 2000, 42, 393-420; Abdel-Malek Z. A., Cell. Mol. Life. Sci. 2001,58, 434-441).

The effects of the melanocortins are mediated by a family of membranereceptors specific to seven transmembrane domains and S-protein-coupled.Five receptor subtypes, named MC1 to MC5, have been cloned andcharacterized to date. These receptors differ in their tissuedistribution and affinity for the different melanocortins, the MC2receptors recognizing only ACTH. The stimulation of the melanocortinreceptors activates the adenylate cyclase with production of cyclic AMP.If the functional roles specific to each of the receptors are nottotally elucidated, the treatment of pathological disorders or diseasescan be associated with an affinity for certain subtypes of receptors.Thus the activation of the MC1 receptors has been associated with thetreatment of inflammations, whereas blocking them has been associatedwith the treatment of cutaneous cancers. The treatment of nutritionaldisorders has been associated with the MC3 and MC4 receptors, thetreatment of obesity by the agonists and the treatment of cachexia andanorexia by the antagonists. Other indications associated with theactivation of the MC3 and MC4 receptors are sexual activity disorders,neuropathic pain, anxiety, depression and drug addiction. The activationof the MC5 receptors has been associated with the treatment of acne anddermatitis.

The applicants have found that the novel compounds of general formula(I) described hereafter possess a good affinity for the melanocortinreceptors. They act preferentially on the MC4 receptors. Said compounds,melanocortin receptor agonists or antagonists, can be used in order totreat pathological states or metabolic diseases, of the nervous ordermatological system in which one or more melanocortin receptors areinvolved such as the following examples: inflammatory states, energyhomeostasis disorders, food intake disorders, weight disorders (obesity,cachexia, anorexia), sexual activity disorders (erectile disorders),pain and more particularly neuropathic pain. Mental disorders can alsobe mentioned (anxiety, depression), drug addiction, skin diseases (acne,dermatitis, cutaneous cancers, melanomas). These compounds can also beused for stimulating nerve regeneration.

DETAILED DESCRIPTION OF THE INVENTION

A subject of the invention is therefore compounds of general formula (I)

in racemic or enantiomeric form or any combinations of these forms andin which:

A represents —CH₂— or —C(O)—;

R₁ represents the hydrogen atom; a (C₁-C₈)alkyl radical optionallysubstituted by hydroxy or one or more identical or different haloradicals; (C₂-C₆)alkenyl; or a radical of formula —(CH₂)_(n)—X₁;

R₂ represents a (C₁-C₈)alkyl radical optionally substituted by hydroxyor one or more identical or different halo radicals; (C₂-C₆)alkenyl; ora radical of formula —(CH₂)_(n)—X₁;

each X₁ represents, independently, a (C₁-C₆)alkoxy, (C₃-C₇)cycloalkyl,adamantyl, heterocycloalkyl, aryl or heteroaryl radical,

-   -   the (C₃-C₇)cycloalkyl, heterocycloalkyl, aryl and heteroaryl        radicals being optionally substituted by one or more identical        or different substituents chosen from: —(CH₂)_(n)—V₁—Y₁, halo,        nitro, cyano and aryl;    -   V₁ represents —O—, —S— or a covalent bond;    -   Y₁ represents a (C₁-C₆)alkyl radical optionally substituted by        one or more identical or different halo radicals;    -   n represents an integer from 0 to 6 and n′ an integer from 0 to        2 (it being understood that when n is equal to 0, then X₁ does        not represent the alkoxy radical);        or R₁ and R₂ form, together with the nitrogen atom to which they        are attached,    -   a heterobicycloalkyl or a heterocycloalkyl optionally        substituted by one or more identical or different substituents        chosen from: hydroxy, (C₁-C₆)alkyl optionally substituted by        hydroxy, (C₁-C₆)alkoxy-carbonyl, heterocycloalkyl and        —C(O)—NV₁′Y₁′ with V₁′ and Y₁′ representing, independently, the        hydrogen atom or a (C₁-C₆)alkyl; or    -   a radical of formula:

R₃ represents a radical of formula —(CH₂)_(s)—R′₃;

R′₃ represents the guanidino radical; a heterocycloalkyl containing atleast one nitrogen atom and optionally substituted by (C₁-C₆)alkyl oraralkyl; a heteroaryl containing at least one nitrogen atom andoptionally substituted by (C₁-C₆)alkyl; or a radical of formula —NW₃W′₃

-   -   W₃ represents the hydrogen atom or (C₁-C₈)alkyl;    -   W′₃ represents a radical of formula —(CH₂)_(s′)—Z₃;    -   Z₃ represents the hydrogen atom, (C₁-C₈)alkyl optionally        substituted by one or more identical or different substituents        chosen from: (C₁-C₆)alkoxy, (C₁-C₆)alkylthio and hydroxy;        (C₂-C₆)alkenyl; (C₃-C₇)cycloalkyl optionally substituted by one        or more identical or different (C₁-C₆)alkyl substituents;        cyclohexene; heteroaryl and aryl;        -   the aryl and heteroaryl radicals being optionally            substituted by one or more identical or different radicals            chosen from: the radical of formula —(CH₂)_(s″)—V₃—Y₃,            hydroxy, halo, nitro and cyano;            -   V₃ represents —O—, —S—, —NH—C(O)—, —NV′₃ or a covalent                bond;            -   Y₃ represents a hydrogen atom or a (C₁-C₆)alkyl radical                optionally substituted by one or more identical or                different halo radicals;            -   V₃′ represents a hydrogen atom or a (C₁-C₆)alkyl;            -   s″ represents an integer from 0 to 4;    -   or Z₃ represents a radical of formula

-   -   s and s′ represent, independently, an integer from 0 to 6;

B represents a condensed, unsaturated, aromatic or non-aromatic mono- orbi-cyclic radical, optionally containing one or more identical ordifferent heteroatoms chosen from O, S and N, and optionally substitutedby one or more radicals, identical or different, chosen from: halo,nitro, cyano, oxy, —X_(B)—Y_(B), and aryl optionally substituted by oneor more substituents chosen from: halo and (C₁-C₆)alkyl optionallysubstituted by one or more identical or different halo radicals;

-   -   X_(B) represents a covalent bond, —O—, —S—, —C(O)—,        —NR_(N)—C(O)—, —C(O—NR_(N)—, —C(O)—O—, —SO₂— or —SO₂NH—;    -   Y_(B) represents the hydrogen atom or a (C₁-C₆)allyl radical        optionally substituted by one or more identical or different        halo radicals;    -   R_(N) represents the hydrogen atom or a (C₁-C₆)alkyl radical;        or a pharmaceutically acceptable salt thereof.

In the definitions given above, the expression halo represents thefluoro, chloro, bromo or iodo radical, preferably chloro, fluoro orbromo. The expression alkyl (unless otherwise stated), preferablyrepresents an alkyl radical having 1 to 6 carbon atoms, linear orbranched, such as the methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-butyl and tert-butyl, pentyl or amyl, isopentyl, neopentyl,2,2-dimethyl-propyl, hexyl, isohexyl or 1,2,2-trimethyl-propyl radicals.The term (C₁-C₈)alkyl designates an alkyl radical having 1 to 8 carbonatoms, linear or branched, such as the radicals containing 1 to 6 carbonatoms as defined above but also heptyl, octyl,1,1,2,2-tetramethyl-propyl, 1,1,3,3-tetramethyl-butyl. The expressionalkyl substituted by hydroxy should be understood to mean any linear orbranched alkyl chain, containing a hydroxy radical positioned along thechain; thus for a chain containing 3 carbon atoms and a hydroxy radical,the examples HO—(CH₂)₃—, CH₃—CH(OH)—CH₂— and CH₃—CH₂—CH(OH)— may begiven.

By alkenyl, unless otherwise stated, is meant a linear or branched alkylradical containing 2 to 6 carbon atoms and having at least oneunsaturation (double bond), such as for example vinyl, allyl, propenyl,butenyl or pentenyl.

The term alkoxy designates the radicals in which the alkyl radical is asdefined above such as for example the methoxy, ethoxy, propyloxy orisopropyloxy radicals but also linear, secondary or tertiary butoxy,pentyloxy. The term alkoxy-carbonyl preferably designates the radicalsin which the alkoxy radical is as defined above such as for examplemethoxycarbonyl, ethoxycarbonyl. The term alkylthio designates theradicals in which the alkyl radical is as defined above such as forexample methylthio, ethylthio. The term guanidino represents the—NHC(═NH)NH₂ radical.

The term (C₃-C₇)cycloalkyl designates a saturated carbonaceousmonocyclic system comprising 3 to 7 carbon atoms, and preferably thecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl rings.The expression heterocycloalkyl designates a condensed monocyclic orbicyclic saturated system containing 2 to 9 carbon atoms and at leastone heteroatom. This radical can contain several identical or differentheteroatoms. Preferably, the heteroatoms are chosen from oxygen, sulphuror nitrogen. As an example of heterocycloalkyl, the following may bementioned: rings with 5 or 6 members containing at least one nitrogenatom such as pyrrolidine, imidazolidine, pyrazolidine, isothiazolidine,thiazolidine, isoxazolidine, oxazolidine, piperidine, piperazine,morpholine, rings with more than 6 members and containing at least onenitrogen atom such as azepane (azacycloheptane), azacyclooctane,diazepane, decahydroisoquinoline (or decahydroquinoline), but also therings containing no nitrogen atom such as tetrahydrofuran(tetrahydrofuryl radical) or tetrahydrothiophene (tetrahydrothienylradical).

The term heterobicycloalkyl designates an non-condensed saturatedbicyclic hydrocarbon system containing 5 to 8 carbon atoms and at leastone heteroatom chosen from nitrogen, oxygen and sulphur. As examples ofheterobicycloalkyl, aza-bicycloheptane and aza-bicyclooctane such as7-aza-bicyclo[2,2,1]heptane, 2-aza-bicyclo[2,2,2]octane or6-aza-bicyclo[3,2,1]octane may be mentioned.

The expression aryl represents an aromatic radical, constituted by aring or condensed rings, such as for example the phenyl, naphthyl,fluorenyl or anthryl radical.

The expression heteroaryl designates an aromatic radical, constituted bya ring or condensed rings, with at least one ring containing one or moreidentical or different heteroatoms chosen from sulphur, nitrogen oroxygen. As examples of a heteroaryl radical, the radicals containing atleast one nitrogen atom such as pyrrolyl, imidazolyl, pyrazolyl,isothiazolyl, thiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazolyl,thiadiazolyl, pyridyl, pyrazinyl, pyrimidyl, pyridazinyl, quinolyl,isoquinolyl, quinoxalinyl, indolyl, benzoxadiazolyl, carbazolyl,phenoxazinyl, thieno-pyridinyl (thieno[2,3-b]pyridine,thieno[3,2-b]pyridine, thieno[2,3-c]pyridine, thieno[3,2-c]pyridine,thieno[3,4-b]pyridine, thieno[3,4-c]pyridine), thieno-pyrazinyl(thieno[2,3-b]pyrazine, thieno[3,4-b]pyrazine) but also the radicals notcontaining a nitrogen atom such as thienyl, benzothienyl, furyl,benzofuryl, dibenzofuryl, dihydrobenzofuryl, dibenzothienyl,thioxanthenyl, or pyranyl can be mentioned.

The term aralkyl (arylalkyl) preferably designates the radicals in whichthe aryl and alkyl radicals are as defined above such as for examplebenzyl or phenethyl.

The expression aromatic, unsaturated, condensed, mono- or bi-cyclicradical, can be illustrated either by the aryl radical as defined abovewhen said aromatic radical does not contain a heteroatom, or by theheteroaryl radical as defined above when said aromatic radical containsat least one heteroatom.

The expression non-aromatic, unsaturated, condensed, mono- or bi-cyclicradical not containing any heteroatom, can be illustrated bycyclopentenyl or cyclohexenyl.

The expression non-aromatic unsaturated, condensed, mono- or bi-cyclicradical containing at least one heteroatom, can be illustrated by theheteroaryl radicals as defined above and in which at least one doublebond is hydrogenated. There may thus be mentioned as examples theradicals associated with the following rings: dihydroindolyl,dihydrothiophene (2,5-dihydrothiophene, 2,3-dihydrothiophene),tetrahydropyridine (2,3,4,5-tetrahydropyridine,1,2,3,6-tetrahydropyridine, 1,2,3,4-tetrahydropyridine),tetrahydro-thieno-pyridine (4,5,6,7-tetrahydro-thieno[3,2-b]pyridine,4,5,6,7-tetrahydro-thieno[2,3-c]pyridine,4,5,6,7-tetrahydrothieno[3,2-c]pyridine), tetrahydropyrimidine(2,3,4,5-tetrahydropyrimidine, 1,2,3,4-tetrahydropyrimidine,1,4,5,6-tetrahydropyrimidine), tetrahydrobenzothiophene(4,5,6,7-tetrahydro-1-benzothiophene), dihydrocyclopentathiophene(5,6-dihydro-4H-cyclopenta[b]thiophene, benzodioxole,dihydro-benzodioxin.

In the present application also, the —(CH₂)_(i) radical (i integer beingable to represent n, n′, s, s′ and s″, as defined above), represents ahydrocarbon chain, linear or branched, with i carbon atoms. Thus the—(CH₂)₃— radical can represent —CH₂—CH₂—CH₂— but also —CH(CH₃)—CH₂—,—CH₂—CH(CH₃)— or —C(CH₃)₂—.

According to the present application also, when a radical has theformula —B-D-E with D representing for example —C(O)—NH—, this meansthat the carbon atom of —C(O)—NH— is linked to B and the nitrogen atomto E.

Preferably, the invention relates to compounds of formula I as definedabove and characterized in that A represents —C(O)—; or apharmaceutically acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that R₁ and R₂ represent, independently,a (C₁-C₈)alkyl; or a pharmaceutically acceptable salt thereof.

Very preferably, the invention relates to compounds of formula I asdefined above, characterized in that R₁ and R₂ represent, independently,a (C₁-C₆)alkyl radical, and more particularly R₁ and R₂ represent,independently, a butyl, pentyl or isopentyl radical; or apharmaceutically acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that R′₃ represents a heterocycloalkylcontaining at least one nitrogen atom and optionally substituted by(C₁-C₆)alkyl or benzyl; or a radical of formula —NW₃W′₃ in which W₃represents the hydrogen atom or a (C₁-C₈)alkyl radical, and W′₃ the Z₃radical and Z₃ represents the hydrogen atom or a (C₁-C₈)alkyl radical;or a pharmaceutically acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B represents a radical chosen from:phenyl, thienyl, pyrrolyl, pyrazolyl, pyridyl, pyrimidyl, pyrazinyl,benzothienyl, thieno-pyridinyl, thieno-pyrazinyl, indolyl, benzofuryl,cyclopentenyl, cyclohexenyl, 1,2,3,6-tetrahydropyridinyl,1,2,3,4-tetrahydropyrimidinyl, 4,5,6,7-tetrahydrothieno[2,3-c]pyridinyl,tetrahydrobenzothienyl and dihydtocyclopentathienyl.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B is optionally substituted by oneor more radicals, identical or different, chosen from: halo, nitro,cyano, oxy, —X_(B)—Y_(B), and phenyl optionally substituted by one ormore substituents chosen from: halo and (C₁-C₆)alkyl optionallysubstituted by one or more identical or different halo radicals;

-   -   X_(B) represents a covalent bond, —O—, —S—, —C(O)—,        —NR_(N)—C(O)— or —C(O)—O—;    -   Y_(B) represents the hydrogen atom or a (C₁-C₆)alkyl radical        optionally substituted by one or more identical or different        halo radicals;    -   R_(N) represents the hydrogen atom; or a pharmaceutically        acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B represents a radical chosen from:phenyl, furyl, thienyl, pyrrolyl, pyrazolyl, pyridyl, thiazolyl,pyrazinyl, benzothienyl, thieno-pyridinyl, thieno-pyrazinyl, indolyl,benzofuryl, cyclohexenyl, 1,2,3,6-tetrahydropyridinyl,tetrahydrobenzothienyl and dihydrocyclopentathienyl.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B is optionally substituted by oneor more radicals, identical or different, chosen from: halo, nitro,cyano, —X_(B)—Y_(B), and phenyl optionally substituted by one or moresubstituents chosen from: halo and (C₁-C₆)alkyl;

-   -   X_(B) represents a covalent bond, —O—, —S—, —C(O)— or —C(O)—O—;    -   Y_(B) represents the hydrogen atom or a (C₁-C₆)alkyl radical; or        a pharmaceutically acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B represents a radical chosen from:phenyl, furyl, thienyl, pyrrolyl pyrazolyl, pyridyl, pyrazinyl,benzothienyl, thieno-pyridinyl, indolyl, benzofuryl, cyclohexenyl,1,2,3,6-tetrahydropyridinyl, tetrahydrobenzothienyl anddihydrocyclopentathienyl.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B is optionally substituted by oneor more radicals, identical or different, chosen from: halo, nitro and—X_(B)—Y_(B);

-   -   X_(B) represents a covalent bond, —O—, —C(O)— or —C(O)—O—;    -   Y_(B) represents a (C₁-C₆)alkyl radical;        and very preferably B is optionally substituted by one or more        radicals, identical or different, chosen from: halo, nitro or        —X_(B)—Y_(B); X_(B) represents a covalent bond or —O— and Y_(B)        represents a (C₁-C₆)alkyl radical; or a pharmaceutically        acceptable salt thereof.

Very preferably, the invention relates to compounds of formula I asdefined above, characterized in that R′₃ represents a heterocycloalkylcontaining at least one nitrogen atom and optionally substituted by(C₁-C₆)alkyl, and in particular the piperidinyl or pyrrolidinyl radical;or a pharmaceutically acceptable salt thereof.

Preferably also, the invention relates to compounds of formula I asdefined above, characterized in that R′₃ represents a heterocycloalkylwith 5 to 6 members and IQ containing a single nitrogen atom andoptionally an oxygen atom; or a radical of formula —NW₃W′₃ in which W₃represents the hydrogen atom or a (C₁-C₆)alkyl radical, W′₃ representsthe Z₃ radical and Z₃ represents the hydrogen atom or a (C₁-C₆)alkylradical; or a pharmaceutically acceptable salt thereof.

Very preferably also, the invention relates to compounds of formula I asdefined above, characterized in that R′₃ represents the piperidinyl orpyrrolidinyl radical, and s represents an integer from 2 to 4; or apharmaceutically acceptable salt thereof.

Very preferably also, the invention relates to compounds of formula I asdefined above, characterized in that B represents a radical chosen from:phenyl, thienyl, pyrrolyl, pyrazolyl, pyridyl, pyrazinyl, benzothienyl,thieno-pyridinyl, thieno-pyrazinyl, indolyl, benzofuryl, cyclohexenyl,4,5,6,7-tetrahydro-thieno[2,3-c]pyridinyl and dihydrocyclopentathienyl.

According to the definitions of the variable groups A, B, R₁, R₂ and R₃,the compounds according to the invention can be prepared in liquid phaseaccording to the different procedures A to C described below.

A. Preparation According to Reaction Diagram:

The compounds of formula (I) according to the invention in which Arepresents —C(O)—, can be prepared according to the following diagram A:

As described in diagram A, the methylated derivative (1) can be oxidizedin carboxylic acid (2) with an aqueous solution of potassiumpermanganate at a temperature of 100° C. for 3 to 6 hours (according tothe procedure of Schmelkes et au, J. Am. Chem. Soc, 1944, 1631), or byan aqueous solution of sodium dichromate in the presence of sulphuricacid at a temperature of 20-90° C. for 1 to 3 hours (according to theprocedure of Howes et al, European J. Med. Chem., 1999, 34, 225-234).The carboxylic acid (2) can be coupled with a primary or secondary aminein the presence of a coupling agent such as diisopropylcarbodiimide(DIC), dicyclohexylcarbodiimide (DCC),1-3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) orcarbonyldiimidazole (CDI) with or without 1-hydroxybenzotriazole (HOBt)in an inert organic solvent such as methylene chloride, tetrahydrofuranor dimethylformamide at ambient temperature for 3 to 24 hours in orderto produce the corresponding amide (3). Treatment of the fluorinated orchlorinated derivative (3) with a primary amine in the presence of aninorganic base such as cesium or potassium carbonate in an inert organicsolvent such as dimethylformamide or acetonitrile at a temperature of20-100° C. for 2 to 48 hours produces derivative (4). The nitro functionof compound (4) is reduced by treatment with stannous chloride dihydratein an inert solvent such as ethyl acetate or dimethylformamide at atemperature of 60-80° C. for 3 to 15 hours, or by catalytichydrogenation in the presence of 10% palladium on charcoal in an inertsolvent such as methanol, ethanol, ethyl acetate or a mixture of thesesolvents, at a temperature of 18-25° C., for 2 to 8 hours in order toproduce dianiline (5). The derivative (5) is then treated with anortho-ester isothiocyanate in the presence of a coupling agent supportedon a resin or not such as diisopropylcarbodiimide ordicyclohexylcarbodiimide or N-methylcyclohexylcarbodiimide N-methylpolystyrene resin, in the presence or not of an organic base such astriethylamine, diisopropylethylamine, sodium methylate, ethylate ortert-butylate, in an inert solvent such as tetrahydrofuran, methylenechloride, or chloroform at a temperature of 20-70° C. for 2 to 72 hours,or under microwaves (Personal Chemistry® equipment), in a sealed tube,at 100° C. for 10 to 30 minutes in order to produce the derivative (6).Alternatively, the derivative (5) can be treated with an ortho-esterisothiocyanate in the presence of yellow mercury (II) oxide and acatalytic quantity of sulphur, in the presence or not of an organic basesuch as triethylamine, diisopropylethylamine, sodium methylate, ethylateor tert-butylate, in a polar solvent such as methanol or ethanol for 2to 24 hours at a temperature of 20-80° C., or under microwaves (PersonalChemistry® equipment), in a sealed tube, at 100° C. for 10 to 30 minutesin order to produce (6).

EXAMPLE A1N,N-bis(3-methylbutyl)-11-oxo-5-(3-piperidin-1-ylpropyl)-5,11-dihydrothieno[3′,2′:4,5]pyrimido[1,2-a]benzimidazole-7-carboxamidehydrochloride

Stage 1: 3-fluoro-4-nitrobenzoic acid

A mixture of 3-fluoro-4-nitrotoluene (10 g, 1 eq) and potassiumpermanganate (25.5 g, 2.5 eq) in water (1 L) is heated under reflux for6 hours then cooled down to ambient temperature. The mixture is filteredon celite and the aqueous phase is washed twice with diethyl ether(2×300 ml). The aqueous phase is acidified, at 0° C., with a solution ofconcentrated hydrochloric acid then concentrated under reduced pressureat 40° C. to a volume of approximately 300 ml. The precipitate formed isfiltered then washed with petroleum ether and dried in order to producethe expected compound in the form of a white solid (6.9 g; 58% yield).

NMR (¹H, 400 MHz, DMSO-d₆): δ 7.93 (m, 2H), 8.25 (m, 1H), 13.95 (m, 1H).

Stage 2: 3-fluoro-N,N-bis(3-methylbutyl)-4-nitrobenzamide

1-hydroxybenzotriazole (HOBt) (8 g, 1.1 eq) in solution in THF (60 ml)and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (ED)C)(11.4 g, 1.1 eq) in solution in chloroform (60 ml) are addedsuccessively to 3-fluoro-4-nitrobenzoic acid (10 g, 1 eq) in solution inanhydrous THF (60 ml). The mixture is stirred for 2 hours at atemperature of approximately 20° C. then diisoamylamine (12.2 ml, 1.1eq) is added. After stirring for 4 hours at a temperature ofapproximately 20° C., the reaction mixture is concentrated under reducedpressure at 40° C. The residue is taken up in dichloromethane (300 ml)and water (100 ml). After decantation and extractions, the combinedorganic phases are washed with salt water, dried over Na₂SO₄ thenconcentrated under reduced pressure at 40° C. Purification by flashchromatography on silica gel (eluent: heptane 100% to heptanel ethylacetate 70:30) produces the expected compound (12.36 g; 71% yield).

MS/LC: MM calculated 324.4; m/z=325.2 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 0.69 (d, 6H), 0.93 (d, 6H), 1.35-1.60 (m,6H), 3.09 (m, 2H), 3.41 (m, 2H), 7.38 (AB, 1H), 7.63 (AB, 1H), 8.21 (t,1H).

Stage 3:N,N-bis(3-methylbutyl)-4-nitro-3-[(3-piperidin-1-ylpropyl)amino]benzamide

A mixture of 3-fluoro-N,N-bis(3-methylbutyl)-4-nitrobenzamide (4 g, 1eq), 3-aminopropylpiperidine (1.9 g, 1.1 eq) and potassium carbonate(3.4 g, 2 eq) in acetonitrile (150 ml) is heated under reflux for 3hours then concentrated under reduced pressure at 40° C. The residue istaken up in dichloromethane (200 ml) and water (80 ml). Afterdecantation and extractions, the combined organic phases are washed withsalt water, dried over Na₂SO₄ then concentrated under reduced pressureat 40° C. Purification of the residue by flash chromatography on silicagel (eluent: ethyl acetate 100% to ethyl acetate/methanol 80:20)produces the expected compound in the form of a yellow oil (5.5 g; 100%yield).

MS/LC: MM calculated 446.6; m/z=447.3 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 0.68 (d, 6H), 0.92 (d, 6H), 1.31-1.69 (m,12H), 1.74 (m, 2H), 2.32 (m, 6H), 3.10 (t, 2H), 3.38 (m, 4H), 6.53 (AB,NH), 6.91 (s, 1H), 8.09 (d, 1H), 8.44 (t, 1H).

Stage 4:4-amino-N,N-bis(3-methylbutyl)-3-[(3-piperidin-1-ylpropyl)amino]benzamide

N,N-bis(3-methylbutyl)-4-nitro-3-[(3-piperidin-1-ylpropyl)amino]benzamide(1 g) in solution in a mixture of ethyl acetate/ethanol 2:1 (100 ml) and10% palladium on charcoal (100 mg) are introduced into an autoclave.After stirring for 3 hours under a hydrogen atmosphere (3 bars) at atemperature of approximately 20° C., the catalyst is eliminated byfiltration on celite and the filtrate is concentrated under reducedpressure at 40° C. in order to produce the expected compound in the formof an oil (910 mg, 97% yield).

MS/LC: MM calculated 416.6; m/z=417.3 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 0.81 (d, 12H), 1.39-1.69 (m, 12H), 1.73(m, 2H), 2.32 (m, 6H), 3.03 (m, 2H), 3.38 (m, 4H), 4.62 (s, 1H), 4.76(s, 2H), 6.36 (s, 1H), 6.42 (AB, 1H), 6.50 (AB, 1H).

Stage 5:N,N-bis(3-methylbutyl)-11-oxo-5-(3-piperidin-1-ylpropyl)-5,11-dihydrothieno[3′,2′:4,5]pyrimido[1,2-a]benzimidazole-7-carboxamidehydrochloride

Methyl 3-isothiocyanatothiophene-2-carboxylate (890 mg), yellow mercuryII oxide (1.6 g) and sulphur (30 mg) are added successively to asolution of4-amino-N,N-bis(3-methylbutyl)-3-[(3-piperidin-1-ylpropyl)amino]benzamide(1.55 g) in methanol (20 ml). The mixture is heated under reflux for 16h. After cooling, the mixture is filtered on celite and the filtrate isconcentrated under reduced pressure at 40° C. Purification of theresidue by flash chromatography on silica gel (eluent: dichloromethane100% to dichloromethane/methanol 95:5) produces the expected compound inthe form of the free base. The corresponding hydrochloride salt isformed by adding a 1N HCl solution in ethyl ether to the free basesolution in ethyl acetate. The precipitate obtained is filtered anddried in order to produce the expected hydrochloride compound (920 mg).

MS/LC: MM calculated=550.3; m/z=549.8 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆) δ 0.68 (s, 6H), 0.95 (s, 6H), 1.25-1.80 (m,12H), 2.27 (m, 2H), 2.80 (m, 2H), 3.18 (m, 4H), 3.35 (d, 2H), 3.45 (m,2H), 4.43 (t, 2H), 7.32 (AB, 1H), 7.35 (AB, 1H), 7.77 (s, 1H), 8.25 (AB,1H), 8.52 (AB, 1H), 9.72 (s, 1H).

EXAMPLE A2N,N-bis(3-methylbutyl)-12-oxo-5-(3-piperidin-1-ylpropyl)-5,12-dihydro[1]benzothieno[3′,2′:4,5]pyrimido[1,2-a]benzimidazole-3-carboxamidehydrochloride

A solution of4-amino-N,N-bis(3-methylbutyl)-3-[(3-piperidin-1-ylpropylamino]benzamide(62 mg) in tetrahydrofuran (1 ml) and a solution of methyl3-isothiocyanatothiophene-2-carboxylate (45 mg) in tetrahydrofuran (1ml) are added successively to a suspension ofN-methylcyclohexylcarbodiimide-N-methyl polystyrene resin (265 mg, 1.7mmol/g charge, 3 eq) in tetrahydrofuran (1 ml), placed in a “PersonalChemistry®” reaction tube. The tube is sealed with a cap, placed in the“Personal Chemistry®” microwave and heated under magnetic stirring at100° C. for 15 minutes. The mixture is then filtered and the filtrate isconcentrated under reduced pressure at 40° C. A solution of the residuein methanol (3 ml) and triethylamine (30 mg) is placed in a “PersonalChemistry®” reaction tube and heated in the microwave under magneticstirring at 100° C. for 10 minutes. The mixture is then concentratedunder reduced pressure at 40° C. Purification of the residue by flashchromatography on silica gel (eluent: dichloromethane 100% todichloromethane/methanol 90:10) produces the expected compound in theform of the free base. The corresponding hydrochloride salt is formed byadding a 1N HCl solution in ethyl ether to the free base solution inethyl acetate. The precipitate obtained is filtered and dried in orderto produce the expected hydrochloride compound (55 mg).

MS/LC: MM calculated=600.4; m/z=599.8 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 50.68 (s, 6H), 0.96 (s, 6H), 1.21-1.81 (m,12H), 2.20 (m, 4H), 3.20 (m, 2H), 3.30 (m, 2H), 3.45 (m, 2H), 4.54 (t,2H), 7.37 (AB, 1H), 7.61 (m, 1H), 7.69 (m, 1H), 7.81 (s, 1H), 8.14 (AB,1H), 8.32 (AB, 1H), 8.58 (AB, 1H), 9.1 (s, 1H).

Preparation of Non-Commercial Isothiocyanates

A primary amine can be converted to isothiocyanate, by treatment withthiophosgene in the presence of a tertiary base such as triethylamine,diisopropylethylamine, in an aprotic solvent such as dichloromethane ortetrahydrofuran, at a temperature of 0-20° C. for 0.1 to 2 hours.

Preparation of methyl 3-isothiocyanatothiophene-2-carboxylate

Thiophosgene (1.1 mL, 1.1 eq) is added dropwise to a solution cooleddown to 0° C. of 3-amino-2-thiophenecarboxylate (2 g, 1 eq) andtriethylamine (3.9 g, 3 eq in tetrahydrofuran (100 ml). The mixture isstirred for 15 min at 0° C. then water (70 ml) and diethyl ether (150ml) are added. After decantation and extractions, the organic phases arecombined, washed with salt water, dried over Na₂SO₄ then concentratedunder reduced pressure at 40° C. Purification of the residue by flashchromatography on silica gel (eluent: heptane 100% to heptane/ethylacetate 7:3) produces the expected compound in the form of a beigepowder (2.15 g, 85% yield).

NMR (¹H, 400 MHz, DMSO-d₆): δ 3.84 (s, 3H), 7.26 (d, 1H), 7.98 (d, 1H).

The following isothiocyanates were prepared according to a proceduresimilar to that described for methyl3-isothiocyanatothiophene-2-carboxylate:

According to reaction diagram A and in a manner similar to the proceduredescribed for the synthesis ofN,N-bis(3-methylbutyl)-11-oxo-5-(3-piperidin-1-ylpropyl)-5,11-dihydrothieno[3′,2′:4,5]pyrimido[1,2-a]benzimidazole-7-catoxamidehydrochloride orN,N-bis(3-methylbutyl)-12-oxo-5-(3-piperidin-1-ylpropyl)-5,12-dihydro[1]benzothieno[3′,2′:4,5]pyrimido[1,2-a]benzimidazole-3-carboxamidehydrochloride, the following compounds have been prepared:

in which R₁R₂N represents one of the following radicals:

represents one of the following radicals:

and R₃ represents one of the following radicals:

B. Preparation According to Reaction Diagram B:

The compounds of formula (I) according to the invention in which Arepresents —C(O)—, can be also prepared according to the followingdiagram B:

As described in diagram B, carboxylic acid (2) can be converted tomethyl ester (7) either by treatment with a trimethylsilyl-diazomethanesolution at a temperature of 0-20° C., or by formation of a carboxylatesalt using an inorganic base such as lithium hydroxide dihydrate orcesium carbonate, at ambient temperature for 30 mm to 2 hours, in aninert organic solvent such as tetrahydrofuran, followed by the additionof dimethylsulphate at ambient temperature and stirring under reflux for5 to 15 hours. The fluorinated or chlorinated derivative (7) can betreated with a primary amine in the presence of an inorganic base suchas cesium or potassium carbonate in an inert organic solvent such asdimethylformamide or acetonitrile at a temperature of 20-100° C. for 2to 48 hours in order to produce the derivative (8). The nitro functionof compound (8) can be reduced by treatment with stannous chloridedihydrate in an inert solvent such as ethyl acetate ordimethylformamide, at a temperature of 60-80° C. for 3 to 15 hours, orby catalytic hydrogenation in the presence of 10% palladium on charcoalin an inert solvent such as methanol, ethanol, ethyl acetate or amixture of these solvents, at a temperature of 18-25° C., for 2 to 8hours, in order to produce dianiline (9). The derivative (9) is thentreated with an ortho-ester isothiocyanate in the presence of a couplingagent supported on a resin or not such as diisopropylcarbodiimide ordicyclohexylcarbodiimide or N-methylcyclohexylcarbodiimide N-methylpolystyrene resin, in the presence or not of an organic base such astriethylamine or diisopropylethylamine, in an inert solvent such astetrahydrofuran, methylene chloride, or chloroform at a temperature of20-70° C. for 2 to 12 hours, or under microwaves (Personal Chemistry®equipment), in a sealed tube, at 100° C. for 10 to 30 minutes in orderto produce the derivative (10). Alternatively, the derivative (9) can betreated with an ortho-ester isothiocyanate in the presence of yellowmercury (II) oxide and a catalytic quantity of sulphur, in the presenceor not of an organic base such as triethylamine, diisopropylethylamine,sodium methylate, ethylate or tert-butylate, in a polar solvent such asmethanol or ethanol for 2 to 24 hours at a temperature of 20-80° C., orunder microwaves (Personal Chemistry® equipment), in a sealed tube, at100° C. for 10 to 30 minutes in order to produce (10). The methyl ester(10) can then be saponified in the presence of an inorganic base such aslithium hydroxide dihydrate in a mixture of polar solvents such as waterand tetrahydrofuran at a temperature of 20 to 70° C. for 3 to 17 hours.The resulting carboxylic acid (11) can be coupled with a primary orsecondary amine in the presence of a coupling agent such asdiisopropylcarbodiimide (DIC), dicyclohexylcarbodiimide (DCC),1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) hydrochloride orcarbonyldiimidazole (CDI), with or without 1-hydroxybenzotriazole (HOBt)in an inert organic solvent such as methylene chloride, tetrahydrofuranor dimethylformamide at ambient temperature for 3 to 24 hours in orderto produce the corresponding amide (6).

C. Preparation According to Reaction Diagram C:

The compounds of formula (I) according to the invention in which Arepresents —CH₂—, can be prepared according to the following diagrams Cand C′:

As described in diagram C, the derivative (4) prepared according toreaction diagram A, can be reduced to the compound (12) using borane orlithium aluminium hydride in an aprotic solvent such as tetrahydrofuranor diethyl ether at a temperature of 0 to 70° C., for 18 to 24 hours.Dianiline (12) can then be treated with an ortho-ester isothiocyanate inthe presence of a coupling agent supported on a resin or not such asdiisopropylcarbodiimide or dicyclohexylcarbodiimide orN-methylcyclohexylcarbodiimide N-methyl polystyrene resin, in thepresence or not of an organic base such as triethylamine ordiisopropylethylamine, in an inert solvent such as tetrahydrofuran,methylene chloride, or chloroform at a temperature of 20-70° C. for 2 to72 hours, or under microwaves (Personal Chemistry® equipment), in asealed tube, at 100° C. for 10 to 30 minutes in order to produce thederivative (13). Alternatively, the derivative (12) can be treated withan ortho-ester isothiocyanate in the presence of yellow mercury (11)oxide and a catalytic quantity of sulphur, in the presence or not of anorganic base such as triethylamine, diisopropylethylamine, sodiummethylate, ethylate or tert-butylate, in a polar solvent such asmethanol or ethanol for 2 to 24 hours at a temperature of 20-80° C., orunder microwaves (Personal Chemistry® equipment), in a sealed tube, at100° C. for 10 to 30 minutes in order to produce (13).

Preparation According to Reaction Diagram C′:

The compounds (13) can also be prepared according to the followingdiagram C′:

As described in diagram C′, the amide (6) prepared according to reactiondiagrams A or B, can be reduced to the corresponding amine (13) usingborane or lithium aluminium hydride in an aprotic solvent such astetrahydrofuran or diethyl ether at a temperature of 0 to 70° C., for 1to 6 hours.

EXAMPLE C18-{[bis(3-methylbutyl)amino]methyl}-10-(3-piperidin-1-ylpropyl)thieno[2′,3′:4,5]pyrimido[1,2-a]benzimidazol-4(10H)-onedihydrochloride

Stage 1:4-{[bis(3-methylbutyl)amino]methyl}-N²-(3-piperidin-1-ylpropyl)benzene-1,2-diamine

A lithium aluminium hydride solution (36 ml; 1N in THF) is addeddropwise to a solution cooled down to 0° C. ofN,N-bis(3-methylbutyl)-4-nitro-3-[(3-piperidin1-ylpropyl)amino]benzamide (1.6 g). The mixture is returned to atemperature of 20° C. then heated under reflux for 6 hours andhydrolyzed with water cooled down to 0° C. followed by a 1N sodasolution. After the addition of dichloromethane, the mixture is filteredon celite. After decantation of the filtrate and extractions, thecombined organic phases are washed with 1N soda then with salt water,dried over Na₂SO₄ and concentrated under reduced pressure at 40° C. inorder to produce the expected compound in the form of an oil (1.23 g,85% yield).

MS/LC: MM calculated=402.7; m/z=403.3 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 0.81 (d, 12H), 1.28 (m, 4H), 1.38 (m, 2H),1.48 (m, 6H), 1.71 (m, 2H), 2.31 (m, 10H), 3.01 (m, 2H), 3.29 (m, 2H),4.28 (m, 2H), 4.6 (m, 1H), 6.30 (AB, 1H), 6.38 (s, 1H), 6.43 (AB, 1H).

Stage 2:8-{([bis(3-methylbutyl)amino]methyl}-10-(3-piperidin-1-ylpropyl)thieno[2′,3′:4,5]pyrimido[1,2-a]benzimidazol-4(10if)-one dihydrochloride

Methyl 2-isothiocyanatothiophene-3-carboxylate (45 mg), yellow mercuryII oxide (65 mg) and sulphur (3 mg) are added successively to a solutionof4-amino-N,N-bis(3-methylbutyl)-3-[(3-piperidin-1-ylpropyl)amino]benzamide(60 mg) in methanol (3 ml). The mixture is heated under reflux for 16 h.After cooling, the mixture is filtered over celite and the filtrate isconcentrated under reduced pressure at 40° C. Purification of theresidue by flash chromatography on silica gel (eluent:dichloromethane100% to dichloromethane/methanol 90:10) produces the expected compoundin the form of the free base. The corresponding hydrochloride salt isformed by adding a 1N HCl solution in ethyl ether to the free basesolution in ethyl acetate. The precipitate obtained is filtered anddried in order to produce the expected hydrochloride compound (30 mg).

MS/LC: MM calculated=536.4; m/z=535.8 (MH+)

NMR (¹H, 400 MHz, DMSO-d₆): δ 0.86 (d, 12H), 1.30 (m, 2H), 1.54 (m, 2H),1.68 (m, 8H), 2.39 (m, 2H), 2.78 (m, 2H), 3.01 (m, 4H), 3.19 (m, 2H),3.38 (m, 2H), 4.37 (t, 2H), 4.48 (m, 2H), 7.37 (AB, 1H), 7.54 (AB, 1H),8.26 (AB, 1H), 8.30 (s, 1H), 8.51 (AB, 1H), 9.97 (s, 1H), 10.96 (s, 1H).

The following compounds have been prepared according to reactiondiagrams C or C′:

in whichR₁R₂N represents one of the following radicals:

represents one of the following radicals:

and R₃ represents one of the following radicals:

A subject of the invention is also a method for the preparation of acompound of formula (I) as defined above, characterized in that thecompound of general formula:

in which A, R₁, R₂, R₃ have the meaning given above, is treated with anortho-ester isothiocyanate of general formula

in which P is a protective group such as methyl, ethyl, tert-butyl and Bhas the meaning given above in the presence of a coupling agent oryellow mercury (II) oxide in the presence of sulphur, in a protic oraprotic solvent, in the presence or not of a base. The reaction can becarried out at a temperature of 50 to 80° C. for a period of 3 to 48hours. The reaction can also be carried out under microwaves, in asealed tube, at a temperature of 80-120° C., for 5 to 30 minutes.

The coupling agent can be supported such asN-methylcyclohexylcarbodiimide N-methyl polystyrene resin or notsupported such as diisopropylcarbodiimide, diethylcarbodiimide ordicyclohexylcarbodiimide. A protic solvent such as methanol or ethanolor an aprotic solvent such as tetrahydrofuran or acetonitrile can beused. The base can be triethylamine, diisopropylethylamine, sodiummethylate, ethylate or tert-butylate.

The compounds I of the present invention possess useful pharmacologicalproperties. Thus it has been discovered that the compounds I of thepresent invention possess a good affinity for certain subtypes ofmelanocortin receptors, in particular MC4 receptors.

The compounds of the present invention can thus be used in differenttherapeutic applications. They can advantageously be used for thetreatment of pathological conditions or diseases in which one or moremelanocortin receptors are involved such as inflammatory conditions,weight disorders (obesity, cachexia, anorexia), sexual activitydisorders (erectile disorders), pain, but also mental disorders(anxiety, depression), drug addiction, skin diseases (acne,dermatitises, melanomas). An illustration of the pharmacologicalproperties of the compounds of the invention will be found hereafter, inthe experimental part.

A subject of the present application is also pharmaceutical compositionscontaining, as active ingredient, at least one product of formula I asdefined above, as well as the pharmaceutically acceptable salts of saidproduct of formula I, in combination with a pharmaceutically acceptablesupport.

By pharmaceutically acceptable salt, is meant in particular additionsalts of inorganic acids such as hydrochloride, hydrobromide,hydroiodide, sulphate, phosphate, diphosphate and nitrate or organicacids such as acetate, maleate, fumarate, tartrate, succinate, citrate,lactate, methanesulphonate, p-toluenesulphonate, pamoate and stearate.Salts formed from bases such as sodium or potassium hydroxide also fallwithin the scope of the present invention when they can be used. Forother examples of pharmaceutically acceptable salts, reference can bemade to “Salt selection for basic drugs”, Int. J. Pharm. (1986), 33,201-217.

A subject of the present application is also the use of the compoundsaccording to the present invention, for the preparation of a medicamentfor the treatment of weight disorders such as obesity, cachexia and moreparticularly cachexia of cancerous pathologies, AIDS cachexia, cachexiain older persons, cardiac cachexia, renal cachexia, rheumatoid arthritiscachexia, and anorexia, the treatment of pain and more particularlyneuropathic pain, mental disorders such as anxiety and depression,sexual activity disorders such as erectile disorders.

The pharmaceutical composition can be in the form of a solid, forexample, powders, granules, tablets, gelatin capsules or suppositories.Appropriate solid supports can be, for example, calcium phosphate,magnesium stearate, talc, sugars, lactose, dextrin, starch, gelatin,cellulose, methyl cellulose, sodium carboxymethyl cellulose,polyvinylpyrrolidine and wax.

The pharmaceutical compositions containing a compound of the inventioncan also be presented in liquid form, for example, solutions, emulsions,suspensions or syrups. Appropriate liquid supports can be, for example,water, organic solvents such as glycerol or the glycols, as well astheir mixtures, in varying proportions, in water, added topharmaceutically acceptable oils or fats. The sterile liquidcompositions can be used for intramuscular, intraperitoneal orsub-cutaneous injections and the sterile compositions can also beadministered intravenously.

All the technical and scientific terms used in the present text have themeaning known to a person skilled in the art. Moreover, all the patents(or patent applications) as well as the other bibliographical referencesare incorporated by way of reference.

EXPERIMENTAL PART

The compounds according to the invention obtained according to theprocedures of examples A, B, C and C′ described previously, are shown inthe table below.

The compounds are characterized by their retention time (rt) and theirmolecular peak determined by mass spectrometry (MH+).

For the mass spectrometry, a simple quadrupole mass spectrometer(Micromass, Platform model) equipped with an electrospray source is usedwith a resolution of 0.8 Da at 50% valley. A calibration is carried outmonthly between the masses 80 and 1000 Da using a calibrating mixture ofsodium iodide and rubidium iodide in solution in an isopropanol/watermixture (1/1 Vol.).

For the liquid chromatography, a Waters system including an in-linedegasser, a Waters 600 quaternary pump, a Gilson 233 plate samplinginjector and a Waters PAD 996 UV detector, is used.

The elution conditions used are the following:

Eluent: A water + 0.04% trifluoroacetic acid; B acetonitrile T (min) A %B % 1 95 5 8.5 5 95 10.5 5 95 10.6 95 5 14.9 95 5 15.0 95 5 Flow rate: 1ml/min; Injection: 10 μl; Column: Uptisphere ODS 3 μm 75*4.6 mm i.d.

These examples are presented to illustrate the above procedures andshould in no case be considered as a limit to the scope of theinvention.

Examples Molecular structures [M + H] + rt (min) 1

550.3 8.9 2

550.4 9.6 3

550.4 9.5 4

544.1 9.1 5

604.4 9.6 6

564.4 9.9 7

530.5 8.1 8

590.4 8.1 9

550.4 8.2 10

536.4 8.0 11

536.4 8.0 12

536.4 8.0 13

496.5 9.2 14

538.5 9.5 15

538.5 9.5 16

536.3 9.2 17

536.5 9.4 18

564.5 9.6 19

552.5 9.3 20

565.5 9.0 21

564.2 10.1 22

548.4 9.6 23

602.3 10.0 24

608.4 9.5 25

606.4 10.4 26

522.3 9.1 27

522.3 9.0 28

508.3 8.9 29

536.3 9.4 30

468.4 9.1 31

482.4 9.1 32

496.4 9.1 33

482.4 9.3 34

598.3 10.0 35

636.5 11.1 36

578.4 10.7 37

592.4 9.9 38

578.2 10.1 39

622.2 10.3 40

578.2 10.2 41

583.4 9.3 42

584.4 9.6 43

548.3 9.0 44

589.4 9.8 45

626.4 10.3 46

644.4 10.4 47

604.3 10.4 48

590.3 10.0 49

660.4 10.7 50

682.5 11.2 51

682.5 11.3 52

591.4 8.5 53

601.3 9.5 54

600.4 10.1 55

618.4 10.1 56

615.4 9.6 57

629.4 9.9 58

592.4 10.1 59

586.3 10.0 60

594.3 9.3 61

533.3 9.0 62

621.1 9.9 63

546.3 8.8 64

606.4 9.4 65

518.3 8.4 66

569.4 9.4 67

532.4 8.9 68

556.4 9.6 69

554.4 9.1 70

505.4 8.5 71

519.4 8.9 72

597.4 9.9 73

643.4 10.3 74

602.4 9.6 75

534.4 9.1 76

623.3 9.7 77

545.4 9.0 78

534.3 9.1Pharmacological Study

The affinity of the compounds of the present invention for the differentsub-types of melanocortin receptors was measured according to proceduresanalogous to those described below for the MC4 receptors.

Study of the Affinity of the Compounds for the MC4 Receptors ofMelanocortins:

The affinity of the compounds of the invention for the MC4 receptors isdetermined by measuring the inhibition of the binding of [¹²⁵I]-[Nle⁴,D-Phe⁷]-α-MSH to membrane preparations of transfected CHO-K1 cells.

The CHO-K1 cells expressing in a stable fashion the human MC4 receptorsare cultured in an RPMI 1640 medium containing 10% of fetal calf serum,2 mM of glutamine, 100 U/ml of penicillin, 0.1 mg/ml of streptomycin and0.5 mg/ml of G418. The cells are collected with 0.5 mM of EDTA andcentrifuged at 500 g for 5 minutes at 4° C. The pellet is resuspended ina phosphate buffered saline (PBS) medium and centrifuged at 500 g for 5minutes at 4° C. The pellet is resuspended in a Tris 50 mM buffer mediumat pH 7.4 and centrifuged at 500 g for 5 minutes at 4° C. The cells arelysed by sonication and centrifuged at 39,000 g for 10 minutes at 4° C.The pellet is resuspended in the Tris 50 mM buffer medium at pH 7.4 andcentrifuged at 50,000 g for 110 min at 4° C. The membranes obtained inthis last pellet are stored at −80° C.

The measurement of the competitive inhibition of the binding of[¹²⁵I]-[Nle⁴, D-Phe⁷]-α-MSH to the MC4 receptors is carried out induplicate using polypropylene 96-well plates. The cell membranes (50 μgof proteins/well) are incubated with [¹²⁵I]-Nle⁴, D-Phe⁷)-α-MSH (0.5 nM)for 90 minutes at 37° C. in a Tris-HCl 50 mM buffer medium, pH 7.4,comprising 0.2% of bovine serum albumin (BSA), 5 mM of MgCl₂, and 0.1mg/ml of bacitracin.

The bonded [¹²⁵I]-[Nle⁴, D-Phe⁷]-α-MSH is separated from the free[¹²⁵I]-[Nle⁴, D-Phe⁷]-α-MSH by filtration through GF/C glass fibrefilters (Unifilter, Packard) pre-impregnated with 0.1% ofpolyethylenimine (P.E.I.), using a Filtermate 196 (Packard). The filtersare washed with Tris-HCl 50 mM buffer, pH 7.4 at 0-4° C. and theradioactivity present is determined using a counter (Packard Top Count).

The specific binding is obtained by subtracting the non-specific binding(determined in the presence of 0.1 μM of Nle⁴, D-Phe⁷-α-MSH) from thetotal binding. The data are analyzed by computer-aided non-linearregression (MDL) and the values of the inhibition constants (Ki) aredetermined.

The agonist or antagonist activity of the MC4 receptors of the compoundsof the present invention was determined by measuring the production ofcyclic AMP by the CHO-K1 cells transfected by the MC4 receptor.

Measurement of the Production of Intracellular Cyclic AMP Via the MC4Receptors:

The CHO-K1 cells expressing the MC4 receptors of the melanocortins arecultured in 384-well plates in an RPMI 1640 medium with 10% of fetalcalf serum and 0.5 mg/ml of G418. The cells are washed twice with 50 μlof RPMI medium comprising 0.2% BSA and 0.5 mM of3-isobutyl-1-methylxanthine (IBMX).

In order to measure the agonist effect of a compound, the cells areincubated for 5 minutes at 37° C. in the presence of 0.5 mM of IBMX,then stimulation of the production of cyclic AMP is obtained by addingthe compound at concentrations comprised between 1 pM and 10 μM induplicate for 20 minutes at 37° C. The antagonist effect of a compoundis measured by inhibiting stimulation of the production of cyclic AMPinduced by Nle⁴, D-Phe⁷-α-MSH at concentrations comprised between 1 pMand 10 μm, in the presence of the compound to be tested, atconcentrations comprised between 1 nM and 10 μM in duplicate for 20minutes at 37° C.

The reaction medium is eliminated and 80 μl of lysis buffer is added.The intracellular cyclic AMP level is measured by a competition testwith fluorescent cyclic AMP (CatchPoint, Molecular Devices).

The tests carried out according to the protocols described above havemade it possible to show that the products according to the presentinvention have a good affinity for the MC4 receptors, the inhibitionconstant K_(i) on these receptors being less than micromolar for themajority of the compounds exemplified.

1. A compound of formula (I)

in racemic or enantiomeric form or any combinations of thereof, wherein:A is —CH₂— or —C(O)—; R₁ is a hydrogen atom; a (C₁-C₈) alkyl radicaloptionally substituted by hydroxy or one or more identical or differenthalo radicals; (C₂-C₆) alkenyl; or a radical of formula —(CH₂)_(n)—X₁;R₂ is a (C₁-C₈) alkyl radical optionally substituted by hydroxy or oneor more identical or different halo radicals; (C₂-C₆) alkenyl; or aradical of formula —(CH₂)_(n)—X₁; each X₁ is, independently, a (C₁-C₆)alkoxy, (C₃-C₇) cycloalkyl, adamantyl, heterocycloalkyl, aryl orheteroaryl radical, the (C₃-C₇) cycloalkyl, heterocycloalkyl, aryl andheteroaryl radicals being optionally substituted by one or moreidentical or different substituents including —(CH₂)_(n)—V₁—Y₁, halo,nitro, cyano or aryl; V₁ is —O—, —S— or a covalent bond; Y₁ representsis a (C₁-C₆) alkyl radical optionally substituted by one or moreidentical or different halo radicals; n is an integer from 0 to 6 and n′an integer from 0 to 2 with the proviso that when n is equal to 0, X₁ isnot an alkoxy radical; or R₁ and R₂ form, together with the nitrogenatom to which they are attached, a heterobicycloalkyl or aheterocycloalkyl optionally substituted by one or more identical ordifferent substituents including hydroxy, (C₁-C₆) alkyl optionallysubstituted by hydroxy, (C₁-C₆) alkoxy-carbonyl, heterocycloalkyl or—C(O)—NV₁′Y₁′ wherein V₁′ and Y₁′ are, independently, a hydrogen atom ora (C₁-C₆) alkyl; or a radical of formula:

R₃ is a radical of formula —(CH₂)_(s)—R′₃; R′₃ is a guanidino radical; aheterocycloalkyl comprising at least one nitrogen atom and optionallysubstituted by (C₁-C₆) alkyl or aralkyl; a heteroaryl comprising atleast one nitrogen atom and optionally substituted by (C₁-C₆) alkyl; ora radical of formula —NW₃W′₃ W₃ is a hydrogen atom or (C₁-C₈) alkyl; W′₃is a radical of formula —(CH₂)_(s)—Z₃; Z₃ is a hydrogen atom, (C₁-C₈)alkyl optionally substituted by one or more identical or differentsubstituents including a (C₁-C₆) alkoxy, (C₁-C₆) alkylthio; hydroxy;(C₂-C₆) alkenyl; (C₃-C₇) cycloalkyl optionally substituted by one ormore identical or different (C₁-C₆) alkyl substituents; cyclohexene;heteroaryl or aryl; the aryl and heteroaryl radicals being optionallysubstituted by one or more identical or different radicals including: aradical of formula —(CH₂)_(s″)—V₃—Y₃, hydroxy, halo, nitro or cyano; V₃is —O—, —S—, —NH—C(O)—, —NV′₃ or a covalent bond; Y₃ is a hydrogen atomor a (C₁-C₆) alkyl radical optionally substituted by one or moreidentical or different halo radicals; V₃′ is a hydrogen atom or a(C₁-C₆) alkyl; s″ is an integer from 0 to 4; or Z₃ is a radical offormula

s and s′ are, independently, an integer from 0 to 6; B is a condensed,unsaturated, aromatic or non-aromatic mono- or bi-cyclic radical,optionally comprising one or more identical or different heteroatomsincluding O, S and N, and optionally substituted by one or moreradicals, identical or different, including halo, nitro, cyano, oxy,—X_(B)—Y_(B), or aryl optionally substituted by one or more substituentsincluding halo and (C₁-C₆) alkyl optionally substituted by one or moreidentical or different halo radicals; X_(B) is a covalent bond, —O—,—S—, —C(O)—, —NR_(N)C(O)—, —C(O)—NR_(N), —C(O)—O—, —SO₂— or —SO₂NH—;Y_(B) is a hydrogen atom or a (C₁-C₆) alkyl radical optionallysubstituted by one or more identical or different halo radicals; R_(N)is a hydrogen atom or a (C₁-C₆)alkyl radical; or a pharmaceuticallyacceptable salt thereof.
 2. The compound according to claim 1 wherein Ais —C(O)—; or a pharmaceutically acceptable salt thereof.
 3. Thecompound according to claim 1, wherein R₁ and R₂ are, independently, a(C₁-C₈) alkyl radical; or a pharmaceutically acceptable salt thereof. 4.The compound according to claim 1, wherein R₁ and R₂ are, independently,a (C₁-C₆) alkyl radical; or a pharmaceutically acceptable salt thereof.5. The compound according to claim 1, wherein R₁ and R₂ are,independently, a butyl, pentyl or isopentyl radical; or apharmaceutically acceptable salt thereof.
 6. The compound according toclaim 1, wherein R′₃ is a heterocycloalkyl comprising at least onenitrogen atom and optionally substituted by (C₁-C₆) alkyl or benzyl; ora radical of formula —NW₃W′₃ wherein W₃ is a hydrogen atom or a (C₁-C₈)alkyl radical, and W′₃ is a Z₃ radical and Z₃ is a hydrogen atom or a(C₁-C₈) alkyl radical; or a pharmaceutically acceptable salt thereof. 7.The compound according to claim 1, wherein B is a radical includingphenyl, thienyl, pyrrolyl, pyrazolyl, pyridyl, pyrimidyl, pyrazinyl,benzothienyl, thieno-pyridinyl, thieno-pyrazinyl, indolyl, benzofuryl,cyclopentenyl, cyclohexenyl, 1,2,3,6-tetrahydropyridinyl,1,2,3,4-tetrahydropyrimidinyl,4,5,6,7-tetrahydro-thieno[2,3-c]pyridinyl, tetrahydrobenzo-thienyl ordihydrocyclopentathienyl.
 8. The compound according to claim 7, whereinB is optionally substituted by one or more radicals, identical ordifferent, including: halo, nitro, cyano, oxy, —X_(B)—Y_(B), or phenyloptionally substituted by one or more substituents including halo or(C₁-C₆) alkyl optionally substituted by one or more identical ordifferent halo radicals; X_(B) is a covalent bond, —O—, —S—, —C(O)—,—NR_(N)—C(O)— or —C(O)—O—; Y_(B) is a hydrogen atom or a (C₁-C₆) alkylradical optionally substituted by one or more identical or differenthalo radicals; R_(N) is a hydrogen atom; or a pharmaceuticallyacceptable salt thereof.
 9. The compound according to claim 1, wherein Bis a radical including phenyl, furyl, thienyl, pyrrolyl, pyrazolyl,pyridyl, thiazolyl, pyrazinyl, benzothienyl, thieno-pyridinyl,thieno-pyrazinyl, indolyl, benzofuryl, cyclohexenyl,1,2,3,6-tetrahydropyridinyl, tetrahydrobenzothienyl ordihydrocyclopentathienyl.
 10. The compound according to claim 9, whereinB is optionally substituted by one or more radicals, identical ordifferent, including halo, nitro, cyano, —X_(B)—Y_(B), or phenyloptionally substituted by one or more substituents including halo or(C₁-C₆) alkyl; X_(B) is a covalent bond, —O—, —S—, —C(O)—, or —C(O)—O—;Y_(B) is a hydrogen atom or a (C₁-C₆) alkyl radical; or apharmaceutically acceptable salt thereof.
 11. The compound according toclaim 1, wherein B is a radical including phenyl, furyl, thienyl,pyrrolyl, pyrazolyl, pyridyl, pyrazinyl, benzothienyl, thieno-pyridinyl,indolyl, benzofuryl, cyclohexenyl, 1,2,3,6-tetrahydropyridinyl,tetrahydrobenzothienyl or dihydrocyclopentathienyl.
 12. The compoundaccording to claim 11, wherein B is optionally substituted by one ormore radicals, identical or different, including halo, nitro or—X_(B)—Y_(B); X_(B) is a covalent bond, —O—, —C(O)— or —C(O)—O—; Y_(B)is a (C₁-C₆) alkyl radical; or a pharmaceutically acceptable saltthereof.
 13. The compound according to claim 12, wherein B is optionallysubstituted by one or more radicals, identical or different, includinghalo, nitro or —X_(B)—Y_(B); X_(B) is a covalent bond or —O— and Y_(B)is a (C₁-C₆) alkyl radical; or a pharmaceutically acceptable saltthereof.
 14. The compound according to claim 1, wherein R′₃ is aheterocycloalkyl comprising at least one nitrogen atom and optionallysubstituted by (C₁-C₆) alkyl; or a pharmaceutically acceptable saltthereof.
 15. The compound according to claim 14, wherein R′₃ is apiperidinyl or pyrrolidinyl radical; or a pharmaceutically acceptablesalt thereof.
 16. The compound according to claim 1, wherein R′₃ is aheterocycloalkyl with 5 to 6 members and comprising a single nitrogenatom and optionally an oxygen atom; or a radical of formula —NW₃W′₃wherein W₃ is a hydrogen atom or a (C₁-C₆) alkyl radical, W′₃ is a Z₃radical and Z₃ is a hydrogen atom or a (C₁-C₆) alkyl radical; or apharmaceutically acceptable salt thereof.
 17. The compound according toclaim 16, wherein R′₃ is a piperidinyl or pyrrolidinyl radical and s isan integer from 2 to 4; or a pharmaceutically acceptable salt thereof.18. The compound according to claim 1, wherein B is a radical including:phenyl, thienyl, pyrrolyl, pyrazolyl, pyridyl, benzothienyl,thieno-pyridinyl, thieno-pyrazinyl, indolyl, benzofuryl, cyclohexenyl,4,5,6,7-tetrahydro-thieno[2,3-c]pyridinyl or dihydrocyclopentathienyl.19. A method for the preparation of a compound of formula (I) accordingto claim 1, comprising treating a compound of general formula:

with an ortho-ester isothiocyanate of general formula:

wherein P is a protective group; in the presence of a coupling agent oryellow mercury (II) oxide in the presence of sulphur, a protic oraprotic solvent, and optionally in the presence of a base.
 20. Apharmaceutical composition comprising a compound according to claim 1 asan active ingredient.
 21. The method according to claim 19, wherein theprotective group (P) is a methyl, ethyl, or tert-butyl group.